High frequency network multiplexed communications over various

ABSTRACT

An improved apparatus for high frequency multiplexed electrical line communication for cable TV, telephone, internet, security and other control applications over the mid and low voltage power lines and directly through the transformers includes a transmitter, a receiver, a modem, a multiplexer and multiple couplers at each of two or more locations along an electrical line. The couplers have capacitive circuits serially connected with an air-core or dielectric-core transformer. The capacitive circuits resonate with the transformer at a preselected frequency. The coupler eliminates noise and is matched to the characteristic impedance of the line at the preselected frequency, which linearizes communication on the line and allows high speed data and voice communication over long distances.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. Ser. No.09/576,981, filed May 23, 2000.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to improved power systemcommunications, and more particularly to apparatus capable ofsimultaneously transmitting and receiving multiple multiplexed digitaldata signals both at high rates and over long distances through powerlines and power line transformers, including AC, DC, coaxial cables, andtwisted pair lines.

[0003] “Power-line Carriers” are well known in the field of power systemcommunications. The principal elements of such power-line carriers aretransmitting and receiving terminals, which include one or more linetraps, one or more coupling capacitors, and tuning and couplingequipment. Detailed information regarding the description and typicalcomposition of conventional power-line carriers may be found inFundamentals Handbook of Electrical and Computer Engineering Volume II:Communication Control Devices and Systems, John Wiley & Sons, 1983, pp617-627, the contents of which are incorporated herein by reference. Asignificant problem associated with prior art power-line carriers istheir requirement for one or more line traps, one or more capacitors,one or more coupling transformers or carrier frequency hybrid circuitsand frequency connection cables.

[0004] All traditional couplers incorporate a ferrite or iron coretransformer which causes signal distortion due to the non-linear phasecharacteristic of the transfer function between the transmit coupler andthe receive coupler. The distortion is created by the presence ofmagnetic core material which exhibits hysteresis. For distributionpower-line carriers, the distortion is particularly severe because thesignal must propagate through at least three such non-linear devices,the distribution transformer and two power-line couplers, that useferrite core transformers. The distortion caused by these non-lineardevices leads to envelope delay distortion, which limits communicationspeeds.

[0005] The major shortcoming of previous designs resulted from the useof ferrite or iron core transformers in the signal couplers. The primarywinding inductance, L1, is altered to some unknown value due to thenon-linearity of the core. This results in a mistuning of the desiredcarrier frequency. Also, the impedance of the primary winding at thedesired carrier frequency is no longer matching the power linecharacteristic impedance. In recognition of this fact, other designsattempt to merely couple a signal onto a power line with a lowtransceiver input impedance by using a large coupling capacitor (approx.0.5 uF). This results in a significant coupling loss of up to 20 dB atthe carrier frequency.

[0006] My co-pending U.S. patent application Ser. No. 09/344,258 (“the'258 Application”) discloses a novel phase shift linear power, phone,twisted pair, and coaxial line coupler for both transmission andreception. The phase shift linear coupler comprises a novel air-core ordielectric core transformer which can be used for phone line, coaxial,LAN and power line communication through power line transformers. Thephase shift linear coupler further comprises an associated couplingcapacitor network in order to achieve resistive matching toapproximately the lowest known value of the line characteristicimpedance and to maximize stable signal transmission onto the line. Thisresonance effectively creates a band pass filter at carrier frequency.The disclosure of the '258 Application is incorporated herein byreference in its entirety.

[0007] The designs of the '258 Application solved many of the problemsof previous designs, which used ferrite or iron couplers that resonatedwith the power line characteristic impedance, resulting in notches, suckouts and non-linear media for communications over various lines such aspower lines. The phase shift linear coupler of the '258 Application doesnot have notches at the communications bandwidth, allowing linearcommunication over a very wide range of frequencies.

[0008] There is still a need, however, for a power line communicationssystem capable of simultaneously transmitting and receiving multipledigital data signals using higher frequencies (e.g., 200 Mhz-500 GHz),thereby permitting communication at high rates using wide bandwidths andover long distances through power lines and power line transformers,including AC, DC, coaxial cables, and twisted pair lines.

BRIEF SUMMARY OF THE INVENTION

[0009] Briefly stated, in a first embodiment, the present invention is acommunications apparatus for communicating multiple electrical signalsthrough one or more electrical lines having a characteristic impedance.The communications apparatus comprises:

[0010] a modulator which modulates the electrical signals to produce amodulated carrier signal having a preselected frequency equal to about200 MHz or greater;

[0011] a transmitter electrically connected to the modulator and havingan output impedance, the transmitter transmitting the modulated carriersignal; and

[0012] a coupler connected between the electrical line and thetransmitter, the coupler matching the output impedance of thetransmitter means to the characteristic impedance of the electrical lineand communicating the modulated carrier signals to the electrical linewithout substantial phase distortion.

[0013] In a second embodiment, the present invention is a communicationsapparatus for communicating electric signals through one or moreelectric lines having a characteristic impedance comprising:

[0014] a modulator which modulates the electric signals to produce amodulated carrier signal having a first preselected frequency equal toabout 200 Mhz or greater;

[0015] a transmitter electrically connected to the modulator and havingan output impedance, said transmitter transmitting the modulated carriersignal;

[0016] a first coupler connected between the electric line and thetransmitter, said coupler matching the output impedance of thetransmitter to the characteristic impedance of the electric line andcommunicating the modulated carrier signal to the electric line withoutsubstantial phase distortion;

[0017] a receiver having an input impedance, said receiver receiving themodulated carrier signal;

[0018] a demodulator electrically connected to the receiver, saiddemodulator producing a demodulated carrier signal having a secondpreselected frequency equal to about 200 Mhz or greater by demodulatingthe modulated carrier signal; and

[0019] a second coupler connected between the electric line and thereceiver for matching the input impedance of the receiver to thecharacteristic impedance of the electric line and communicating themodulated carrier signal to the receiver without significant phasedistortion.

[0020] In a third embodiment, the present invention is a communicationsapparatus for communicating electric signals through one or moreelectric lines having a characteristic impedance comprising:

[0021] a first modem which produces a first modulated carrier signalhaving a first preselected frequency equal to about 200 MHz or greaterand demodulates a second modulated carrier signal having a secondpreselected frequency equal to about 200 MHz or greater;

[0022] a first transmitter having an output impedance, said transmitterconnected to the first modem and transmitting the first modulatedcarrier signal;

[0023] a first receiver having an input impedance, said receiverconnected to the first modem and receiving the second modulated carriersignal;

[0024] a first coupler connected between the electric lines and thefirst transmitter and the first receiver, said first coupler matchingthe output impedance of the first transmitter and the input impedance ofthe first receiver to the characteristic impedance of the electric linesand communicating the first and second modulated carrier signals withoutsubstantial phase distortion;

[0025] a second modem which produces the second modulated carrier signaland demodulates the first modulated carrier signal;

[0026] a second transmitter having an output impedance, said transmitterconnected to the second modem and transmitting the second modulatedcarrier signal;

[0027] a second receiver having an input impedance, said receiverconnected to the second modem and receiving the first modulated carriersignal; and

[0028] a second coupler connected between the electric lines and thesecond transmitter and the second receiver, said second coupler matchingthe output impedance of the second transmitter and the input impedanceof the second receiver to the characteristic impedance of the electriclines and communicating the first and second modulated carrier signalswithout substantial phase distortion.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0029] The foregoing summary, as well as the following detaileddescription of preferred embodiments of the invention, will be betterunderstood when read in conjunction with the appended drawings. For thepurpose of illustrating the invention, there is shown in the drawingsembodiments which are presently preferred. It should be understood,however, that the invention is not limited to the precise arrangementsand instrumentalities shown.

[0030] In the drawings:

[0031]FIG. 1 is a graphical illustration of the characteristic impedanceto the power line of the coupler of the present invention;

[0032]FIG. 2 is a schematic block diagram of a power-line communicationwide area network according to the present invention;

[0033]FIG. 3 is a schematic diagram of a half-duplex power line modemaccording to the present invention;

[0034]FIG. 4 is a schematic diagram of a full-duplex power line modemaccording to the present invention;

[0035]FIG. 5 is a schematic block diagram of a power line communicationsapparatus in accordance with the present invention;

[0036]FIG. 6 is a schematic diagram of a modulator at a first frequencyfor use in the power line communications apparatus of FIG. 5;

[0037]FIG. 7 is a schematic diagram of a modulator at a second frequencyfor use in the power line communications apparatus of FIG. 5;

[0038]FIG. 8 is a schematic diagram of a demodulator at a firstfrequency for use in the power line communications apparatus of FIG. 5;

[0039]FIG. 9 is a schematic diagram of a demodulator at a secondfrequency for use in the power line communications apparatus of FIG. 5;

[0040]FIG. 10 is a schematic diagram of an Ethernet interface for use inthe power line communications apparatus of FIG. 5;

[0041]FIG. 11 is a schematic diagram of a coupler for use in the powerline communications apparatus of FIG. 5 at a first set of frequencies;

[0042]FIG. 12 is a schematic diagram of a coupler for use in the powerline communications apparatus of FIG. 5 at a second set of frequencies;and

[0043]FIG. 13 is a schematic diagram of a power supply for use in thepower line communications apparatus of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

[0044] The present invention presents improvements to the phase shiftlinear coupler of the '258 Application. It has been discovered thatusing higher frequencies (1-500 GHz) with an air-core or dielectric corecoupler produces better results because it has wider bandwidth and cantransmit for further distances. The higher frequency signals will createa magnetic field around any type of wire and will travel along thesurface of a power line like a magnetic wave and jump transformers.Therefore the transmission of such high frequency signals can beachieved for long distances with wide bandwidth.

[0045] In a controlled environment like a coax cable, a high frequencysignal of 1 GHz or more will travel only a short distance before it willdisappear. This is because a coax cable has a high fixed serialinductance L and a parallel capacitance C which result in a strong lowpass filter that can eliminate signals of every frequency at a certaindistance. Also, a coax cable can only create a small magnetic fieldaround the middle conductor because it is closely shielded.

[0046] A different environment is presented by power lines, which do notsimply go from one point to another, but rather are in a starconfiguration. Power lines do not have fixed L and C values andtherefore the power line is a weaker low pass filter than the coaxcable. Power lines are also not shielded, and therefore the power lineconductor can create a larger magnetic field around the wire than in acoax cable. Additionally, the characteristic impedance Zo of the powerlines changes in time and in location and the number of wires connectedto each other also varies at various points in the power distributionnetwork. Accordingly, the propagation of electric/magnetic fields fromdigital signals down the power lines will not be eliminated and suchsignals can travel further than in the coax cable. High frequencysignals can also jump power line transformers, which look like a bigparallel capacitor to the signal, without much loss of signal strengthif matching to the power line according to the present invention asdescribed herein is used.

[0047] The importance of the coupler of the present invention is that itcan remain a matching device to the power line characteristic impedance.As in the '258 Application, the coupler of the present inventioncomprises an air-core or dielectric-core transformer and a couplingcapacitor, Ceq. Any impedance change on the primary winding of thetransformer does not reflect much to the secondary winding of thetransformer and vice versa. Therefore, the only impedance that will beseen by the power line is the primary winding resonated with thecapacitor Ceq. Such serial resonance will create a low impedance, whichwill be close to 1 ohm. As the frequency is increased, the impedancewill increase also to approximately 100-200 ohms, depending on whichimpedance is the best to match the power line characteristic impedance,and how much bandwidth is needed.

[0048] For example, FIG. 1 shows the coupler characteristic impedance tothe power line. If the power line impedance is 100 ohms at F1 then 6 dBmatching from the coupler will be from 40 ohms to 50 ohms (F4) to 200ohms(F3), which will cover a wide bandwidth from F3 to F4. By contrast,if the power line characteristic impedance is only 10 ohms, the 6 dBmatching will be from 5 to 20 ohms, resulting in a smaller bandwidth.Lowering the coupler impedance can result in wider bandwidth matching inlow characteristic impedance (e.g., 10 ohms) power lines.

[0049] As discussed in the '258 Application, a significant advantage ofthe coupler of the present invention is the phase linearity achieved.Power lines have local impedances every couple of feet at differentfrequencies. The best matching to the power line can be achieved byusing inductor (L) and capacitor (C) components that do not includeferrite and iron cores because the power line consists of L's and C's.Moreover, reflections occur at the end of each unterminated line.Ferrite or iron core couplers also have self resonances around thecommunications bandwidth of interest. The self resonance and thereflection in the power lines create variable bandwidth notches. Bycontrast, the air-core or dielectric-core coupler of the presentinvention self resonance is at a much higher frequency then thefrequency band of interest, and the air-core coupler matches the localcharacteristic impedance of the power line. Therefore, reflections donot create notches at the frequency band of interest.

[0050] 6 to 10 dB flatness of bandwidth is achieved by using the couplerof the present invention to match to the power line. This matching canbe achieved when the power line characteristic impedance is between therange of half of the coupler primary impedance and twice the couplerprimary impedance. For example, the primary impedance of the couplerwill range from 1 to 100 ohms for the frequency band 18-30 MHz. Assumingthat the power line impedance is 50 ohms at 22 MHz and 10 ohms at 20MHz, around 20 MHz we will have a matching from 25 to 100 ohms whichwill cover frequencies between approximately 21 to 30 MHz. Assuming thatthe coupler primary impedance at 20 MHz is about 20 ohms, matching willbe achieved from 18 to about 22 MHz. The total matching will be from 18to 30 MHz of 10 dB bandwidth, and there will be no notch.

[0051] Power lines have a typical impedance of 50 to 100 ohms forunderground lines and 100 to 500 ohms for overhead lines. However,circuit breakers and underground substations with lots of feeders maycreate as low as a 1 ohm power line characteristic impedance at theirlocation. The coupler is designed to accommodate the most common localimpedance of the power line. For example, if the power linecharacteristic impedance is 80 ohms, then 6 dB matching can be achievedwith the air-core coupler of the present invention from 40 to 160 ohmsat any location. The power line must be matched locally because thelocal impedance of the power line changes every few feet. Since the 120Vpower line characteristic impedance is known to be, for example 80 ohms,therefore 80 ohms will be a good match at any 120V location.

[0052] Since the secondary impedance is not changed significantly by thechange of the power line characteristic impedance, transmitter andreceiver matching can be achieved at around 50 ohms. Both sides of thetransformer are matched regardless of the change of impedance on thepower line. The secondary of the transformer is matched by thetransmitter or receiver. The impedance change on the primary of thetransformer does not reflect to the secondary. Therefore, 45-50 ohmsmatching is achieved all of the time to the transmitter and the receiverregardless of the impedance changes in the power lines.

[0053] For higher frequencies (e.g., 200 Mhz-500 GHz), the structure ofthe air-core or dielectric core transformer differs from that of the'258 Application. The coupler may no longer be two coaxial solenoids orair-coils of different diameter wrapped with magnet wire, but instead ismuch smaller and resembles a chip which is filled with any type ofplastic or non-conductive material, such as resin, glue material,ceramic or any other hard non-conductive material (“chip material”). Thecoupler preferably comprises very thin conductive plates separated bychip material. The plates are preferably made from copper, but can alsobe made from silver, gold, or any other conductive material, whether itis active or passive. The plates can be any shape (e.g., square,rectangular, round, etc.) but are preferably circular. The size of suchlayered air-core transformers will depend on the frequency of usage. Forexample, a 30 GHz coupler primary diameter will be less then 1millimeter, the layer thickness will be less then about 0.1 millimeter,which results in about a 0.3 nH inductance. Similarly, the thinrectangular copper plate sizes will be around a couple of millimeterslong, 0.1 millimeters thick and the primary and secondary inductors willbe about 0.5 millimeters away from each other, on top of each other.Consequently, such devices will look like a very small capacitor.However, the present invention uses the end to end inductor values toresonate the capacitor for matching the power line characteristicimpedance.

[0054] Alternatively, the plates can be formed directly in a chip bydeposition of metallic layers or through doping silicon. Doped siliconis conductive when it is active—e.g., a DC level of voltage turns on atransistor to make it an active device. Thus, the plates when formed ofdoped silicon may take the form of some type of active device such as atransistor or a diode. Of course, it will be appreciated that otherdesigns of air-core or dielectric-core transformers can be used withoutdeparting from the spirit or scope of the present invention. Forexample, a piece of coax cable can be used as an air-core transformer.The shield of the coax cable is the primary of the transformer and theinside wire is the secondary of the transformer. This coax type ofair-core transformer can be used for very high frequency communicationsabove 500 MHz. Similarly two copper or iron pipe-like cylinders (oraluminum or copper foil) can be placed inside each other. The outsidecylinder or foil is the primary of the air-core transformer, and theinner cylinder or foil is the secondary. This design can also be usedover 100 MHz.

[0055] Moreover, recent work has been done in creating solid-statetransformers for the conversion of mid-voltage AC on the order of 7.6 kVto 120 VAC using technology similar to that used in switching regulatorsfor DC to DC conversion. The technology used in these solid-statetransformers is called the Gate Drive Control of Transistors Gate drivecircuits and is well known, and need not be described in detail herein.These transformers are designed with so-called “solid state”technology—namely, they rely primarily on semiconductor components suchas transistors and integrated circuits instead of the heavy copper coilsand iron cores of conventional transformers. Such solid-statetransformers can also be used in the couplers of the present invention.One of ordinary skill in the art will also appreciate that other moresimple integrated circuits can also be used to create transformers foruse in the coupler of the present invention. Today's integrated circuitsusing active transistors can simulate and/or create an air-coretransformer that can have the necessary inductance and capacitancevalues to work exactly as a regular air-core transformer.

[0056] Although the structure of the coupler as described above differsfrom that disclosed in the '258 Application, the function of the coupleris the same. The plates (or cylinders or foils) of the coupler of thepresent invention are inductively and capacitively coupled creating anair-core or dielectric-core transformer. The coupling of the primary andsecondary of the transformer varies with frequency, however. The primaryand secondary are coupled about equally magnetically and electrically(i.e., capacitively and inductively coupled) below 100 MHz of frequencyand more inductively coupled (magnetically) at frequencies higher than100 MHz. At frequencies on the order of 100 GHz, the primary andsecondary of the transformer will be mostly inductively coupled.

[0057] As described in detail in the '258 Application, thecommunications apparatus of the '258 Application has numerousapplications. The high frequency couplers of the present inventionextend this functionality by allowing much higher data transmissionrates. For example, the present invention can use high frequencycarriers on the order of 200 Mhz-50 GHz for transmission over the powerlines. Using the air-core or dielectric-core coupler technology of thepresent invention, up to at least 1 Gbps of communication speed can beachieved over the power lines.

[0058] Referring now to the drawings, wherein like numerals designatelike or corresponding parts throughout each of the several views, thereis shown in FIG. 2 a block diagram of a power-line communication widearea network (WAN) according to the present invention.

[0059] An Ethernet router 12 is connected to a network backbone, such asthe Internet or an Intranet using a HUB or switch (not shown) like theNetwork Peripheral's NuWave 3 layer line of products. The router 12 isalso connected to a power line modem 14, which in turn is connected to amid voltage power line coupler 16, which couples the signals from themodem 14 onto the 11 KV power line 18 at a substation 20.

[0060] Those of skill in the art will appreciate that the Ethernetrouter 12 could be connected to other devices in other applicationswithout departing from the spirit or scope of the present invention. Forexample, other applications include (1) Ethernet wide area networks withother servers where the backbone is connected to another network; (2)telephone service applications where the backbone is connected to atelephone center and to a time division multiplexer that will establishmultiple telephone lines over the power line; and (3) televisionapplications where the backbone is connected to a TV broadcastingstation that will digitally transmit several TV stations over the powerline.

[0061] The Ethernet router 12 is a standard Ethernet router. The powerline modem 14, through the mid voltage power line coupler 16, modulatesand demodulates the Ethernet signals onto the 11 KV power line 18. Thedesign of the power line modem 14 is discussed in detail below. The midvoltage power line coupler 16 is preferably about 0.5 meters high and0.2 meters in diameter, placed in a ceramic insulator and stuffed withresin. A dielectric-core transformer is preferably used for the coupler,which, as explained above, can take the form of two small pieces ofplate laid capacitively on top of each other for high frequencyoperation. Of course, any of the other high frequency transformerdesigns discussed above could also be used in the mid voltage power linecoupler 16 without departing from the spirit or scope of the presentinvention.

[0062] The high frequency signal, preferably a 100 Mbps or greaterEthernet signal, propagates over power lines 18 and through one or moredistribution transformers 22, 24 by magnetic waves and onto the 110-220Vlow voltage power lines 26. The signal is picked up by one or more powerline modems 14 through low voltage couplers 28. The low voltage couplers28 and the power line modems 14 are preferably placed on the low voltagepower lines 26 before the power meters (not shown) going into buildings30. The power line modems 14 are identical to the power line modems 14coupled to the power lines 18. The low voltage couplers 28 can bedesigned as described in the '258 Application, and are smaller than themid voltage power line coupler 16. The low voltage couplers 28 use highfrequency air-core or dielectric-core transformers as described above.

[0063] Ethernet switches (HUBs) 32 are coupled to the power line modems14. The Ethernet switches 32 distribute the Ethernet data over the powerlines into buildings 30 using a power-line communication local areanetwork (LAN) according to the present invention as described below.

[0064] The power line modems 14 preferably all use a 1.35 GHz frequencyfor both transmission and reception. This carrier frequency willcommunicate over the distribution transformers 22, 24 from the midvoltage power lines 18 (7 to 35 KV) to the low voltage power lines 26(110 to 240 V) to the buildings 30. 100 Mpbs or 10 Mbps Ethernet datacan be transmitted using this carrier frequency. Those of skill in theart will appreciate that other carrier frequencies, such as 2.7 GHz or3.5 GHz can be used without departing from the spirit or scope of thepresent invention. Thus the system an communicate carrier frequencysignals through distribution transformers at greater than 100 Mbps atcarrier frequencies of 200 MHz or higher. The carrier frequency can becarried on low voltage (e.g. 120 volt), mid voltage (e.g. 3-35 KV) orhigh voltage (e.g. 69-750 KV) power lines.

[0065] In an alternate embodiment, a carrier frequency of 30 GHz or morecan be used to transmit Ethernet data of 10 Mbp, 100 Mbps, 1 Gbps ormore. When a carrier frequency of this magnitude is used, the power-linecommunication wide area network (WAN) of the present invention is ableto communicate all the way from the substation 20 into the buildings 30without the need of stopping at the power meters outside the buildings30. Therefore, the power line modems 14 and low voltage couplers 28 donot need to be placed on the low voltage power lines 26 before the powermeters (not shown) going into buildings 30. Rather, the power linemodems 14 and low voltage couplers 28 can be placed inside of thebuildings 30.

[0066] Those of skill in the art will also understand that although thepresent embodiments are described using the Ethernet protocol totransmit and receive data, any other data protocol can be used with thepower-line communication wide area network (WAN) of the presentinvention without departing from the spirit or scope of the presentinvention.

[0067] Referring now to FIG. 3, a presently preferred configuration forthe power line modem 14 is shown. Physical Ethernet interface 38connects the power line modem 14 to an Ethernet card or HUB or repeater(not shown), and can comprise any appropriate connection including atwisted pair connection. Ethernet data (e.g., Manchester coded data) isprovided from the interface 38 to CPU 40, such as a Motorola MPC855T,which converts the coded data to and from the parallel bus interface 42.Memory 44 is used to buffer the data on the parallel bus interface 42.

[0068] A Field Programmable Gate Array (FPGA) 46, preferably a XilinxVirtex XCV100-FG256, connects to the parallel bus interface 42 andprovides control for the power line modem 14 as well as performing themultiple modulation and demodulation of data that is transmitted andreceived, respectively. EPROM 48 stores program instructions for FPGA 46and the CPU 40. The FPGA 46 controls transmit/receive switch 36, whichis connected to coupler 34 and the power lines 48 over which the datafrom power line modem 14 is carried. The interface of coupler 34 to thepower lines 48 as well as the structure of coupler 34 are explained indetail in the '258 Application. As noted above, however, a highfrequency air-core or dielectric-core transformer of the presentinvention must be used in the coupler 34.

[0069] Circuitry is provided to interface signals to and from the FPGA46. For transmission, a signal leaves the FPGA 46 and passes throughanalog to digital (A/D) converter 50. Up conversion to the carrierfrequency is performed by mixer 58 and local oscillator 52. Amplifier 56and filters 54 are used to interface the resulting signal with thecoupler 34. Similarly, for reception, a signal passes through filters 54and amplifiers 56, and is down converted by mixer 58 and localoscillator 58. Automatic gain control (AGC) is performed by AGC circuit62, and then the signal is digitized by analog to digital (A/D)converter 60 for transmission to the FPGA 46. The power line modem ofFIG. 3 is a half-duplex modem, so the carrier frequency used fortransmission and reception is the same. Those of skill in the art willrecognize that the AGC and mixer up/down conversion can be performed bythe FPGA without the need of additional circuitry.

[0070] The filters 54 may be SAW filters or filters can be programmedinto the FPGA 46. The BPF (band pass filter) may be a SAW filter as wellas the LPF's (Low pass filters) 54.

[0071] The FPGA 46 can be programmed to use any type of modulationdesired. The FPGA 46 could be programmed to use FM, FSK, QPSK, 16QAM,CDMA, ADSL, FDM, orthogonal frequency division multiplexed (OFDM) or anyother type of modulation without departing from the spirit or scope ofthe present invention. It will also be appreciated that the particularmodel of the FPGA 46 or CPU 40 can be changed without departing from thepresent invention. In fact, the FPGA 46 can be replaced by other typesof DSP processors as discussed in the '258 Application.

[0072] Instead of one modulated carrier frequency, multiple modulatedcarrier frequencies can be used. This is accomplished by adding multiplemodulators and demodulators coupled into the programmable FPGA 46 usingSAW filters to thereby create either a frequency division multiplexed(FDM) or orthogonal frequency division multiplexed (OFDM) system. Thisis accomplished by programming the FPGA device 46. Device 46, which asindicated, has both multiplexing and demultiplexing capability. It is astraightforward matter to program device 46 to be responsive to multiplemodulators. The advantage is that the noise level is lower over a narrowbandwidth for each of several modulated signals and the usage of FMD(Frequency Division Multiplexing) or OFDM can further increase thetransmission speed over the power line.

[0073]FIG. 4 shows a full-duplex implementation of a power line modem14. The structure of the modem 14 is almost identical to the half-duplexmodem 14 as shown in FIG. 3, with the exception of the interface betweenthe modem 14 and the power lines 48. As seen in FIG. 4, thetransmit/receive switch 36 has been removed. Instead, one coupler 34operating at a first frequency F1 is used for transmission, and a secondcoupler 34 operating at a second frequency F2 is used for reception. Forexample, 1.2 and 1.6 GHz frequencies could be used to simultaneouslytransmit and receive over the power lines 48. In addition to thestructural difference in the modem 14, the software program stored inEPROM 48 for the FPGA 46 would also need to be changed to reflect fullduplex operation at two different frequencies.

[0074] The full duplex system shown in FIG. 4 can be programmed to usemultiple modulators and demodulators as described in respect to FIG. 3.

[0075] Turning now to FIG. 5, there is shown a block diagram of apower-line communications apparatus 10 according to the presentinvention for use in a power-line communication local area network(LAN). The communications apparatus 10 shown is coupled to a pair ofpower-lines 48. The communications apparatus 10 generally comprises amodulator 64, a demodulator 66, an Ethernet interface 68, a coupler 34and a power supply 70. The communications apparatus 10 connects to anEthernet card, HUB or switch (not shown) and sends Ethernet data overthe power lines 48 in full duplex.

[0076] In operation, a first communications apparatus 10, designated theMaster unit, is coupled to power lines 48 and transmits at a firstfrequency F1 and receives at a second frequency F2. A secondcommunications apparatus 10, designated the Slave unit, is also coupledto power lines 48 and transmits at the second frequency F2 and receivesat the first frequency F1. For purposes of example only, the apparatusdescribed below uses 250 MHz for F1 and 350 MHz for F2 to provide a 10Mbps Ethernet signal over the power lines. It will of course beappreciated by those of skill in the art that other frequencies could beused without departing from the spirit or scope of the presentinvention. For example, frequencies in the 2.44 GHz and 5.8 GHz bands,which are license free frequency bands for communications, could be usedto provide a 100 Mbps Ethernet signal over the power lines.

[0077] Details of the modulator 64 for the Master unit (e.g.,transmission at 250 MHz) are shown in FIG. 6. The modulator 64 ispreferably an FM modulator comprising an oscillator 76, modulator 74 andassociated capacitors and inductors connected as shown. The modulator 64also includes RF transformer 72 and associated circuitry as shown tointerface from the Attachment Unit Interface (AUI) port of the Ethernetinterface 68. The Ethernet input signal is conveyed from the transformerthrough the oscillator/modulator circuitry 74, 76 and then through an LCfilter circuit for output of the modulated signal. The values of thecapacitors and inductors are chosen based on the carrier frequency,which in the case of the Master unit is 250 MHz.

[0078]FIG. 7 shows the modulator 64 for the Slave unit (e.g.,transmission at 350 MHz). The Slave modulator 64 is identical to theMaster modulator 64 except for the values of the inductors andcapacitors in the LC filter circuit. The values of the inductors andcapacitors in the Slave modulator 64 are chosen based on the 350 MHzcarrier frequency.

[0079] Details of the demodulator 66 for the Master unit (e.g.,reception at 350 MHz) are shown in FIG. 8. The FM modulated input signalis first sent through two RF amplifiers 78 and associated circuitry asshown between the amplifiers 78 comprising Blinch filters in order toseparate the noise and the other carrier frequency from the modulatedinput signal. The LC values in the Blinch filters are chosen based onthe carrier frequencies used in the communications apparatus 10. Thefiltered, modulated signal is then coupled into FM detector circuit 82through RF transformer 80. The FM detector circuit 82 is preferably anMC13155D. The output of the FM detector circuit 82 is then passedthrough fast amplifiers 84 and filters 86 to generate an output signalof the recovered Ethernet data from the modulated input signal.

[0080]FIG. 9 shows the demodulator 66 for the Slave unit (e.g.,reception at 250 MHz). The Slave demodulator 66 is identical to theMaster demodulator 66 except for the values of the inductors andcapacitors in Blinch filters used on the modulated input signal. Thevalues of the inductors and capacitors in the Slave demodulator 66 aredifferent because of the different carrier frequency that is beingfiltered out of the modulated input signal.

[0081] The embodiment of the demodulator 66 described above is limitedto an Ethernet speed of 10 Mpbs because of the use of an MC13155D FMdetector circuit and carrier frequencies of 250 MHz and 350 MHz. Thebandwidth of the demodulator 66 can be increased to an Ethernet speed of100 Mbps by using an FM detector circuit 82 capable of operating at afrequency band greater than 200 MHz and also using carrier frequenciesgreater than 1 GHz.

[0082] Turning to FIG. 10, the details for the Ethernet interface 68 forboth the Master and Slave units are shown. Two alternative interfacesare embodied in the Ethernet interface 68. First, an AUI interface isprovided to an Ethernet HUB or switch through connector 88. Two lines 90run from the connector 88 directly to the modulator 64, and the outputof the demodulator 66 is coupled to the connector 88 using RFtransformer 92. Alternatively, the communications apparatus 10 canconnect to an Ethernet HUB or switch using a twisted-pair Ethernet RJ-45connector 94. When RJ-45 connector 94 is used, integrated circuit 96,which is a 10Base-T transceiver or Ethernet twisted-pair/AUI Adapter,preferably a ML4658CQ, and associated circuitry as shown are used tointerface the RJ-45 connector 94 with the AUI port of connector 88.

[0083] Referring to FIG. 11, the coupler 34 for use in the Mastercommunications apparatus 10 is shown. For transmission to the powerlines 48, the output of the modulator 64 is first passed through RFamplifier 96 and low pass filter 98. The signal is then sent to a highfrequency air-core or dielectric-core coupler of the present inventioncomprising air-core or dielectric-core transformer 100 and couplingcapacitor (Ceq) 102. The transformer 100 and coupling capacitor 102couple the signal to the power lines 48. The LC values in the low passfilter 98 are chosen based on the carrier frequency. The capacitorvalues of the coupling capacitor (Ceq) 102 are chosen to provide a 50ohms impedance match between the power lines 48 and the RF amplifier 96.

[0084] For reception of signals from the power lines 48, a highfrequency air-core or dielectric-core coupler of the present inventioncomprising air-core or dielectric-core transformer 104 and couplingcapacitor (Ceq) 106 first couples the input signal from the power lines48. The input signal is then sent through an RF amplifier 108 and Blinchfilter 110 for output to the demodulator 66. As on the transmissionside, the LC values in the Blinch filter 110 are chosen based on thecarrier frequency. The capacitor values of the coupling capacitor (Ceq)106 are chosen to provide a 50 ohms impedance match between the powerlines 48 and the RF amplifier 108.

[0085]FIG. 12 shows the coupler 34 for the Slave communicationsapparatus 10. The Slave coupler 34 is identical to the Master coupler 34except for the values of the inductors and capacitors in Blinch filter110 and low pass filter 98 as well as the capacitor values of thecoupling capacitors (Ceq) 102, 106. The values of the these inductorsand capacitors in the Slave coupler 34 are different because the carrierfrequencies for transmission and reception of signals from the powerlines 48 are reversed from the Master communications apparatus 10.

[0086] Finally, FIG. 13 shows the power supply 70 for use with thecommunications apparatus 10. AC power is taken from the power lines 48and passed through beads 112 in order to isolate the impedance of thepower transformers 114 from the impedance of the power lines 48. This isdone in order to provide a more stable bandwidth over the power linesand a bigger signal level. DC power is produced using power transformers114 and rectifiers 116. Finally, DC outputs of different voltages neededin the communications apparatus 10 are produced using voltage regulators118. As seen in FIG. 13, separate power transformers 114, rectifiers 116and voltage regulators 118 are used to provide power for thetransmission side and the reception side of the communications apparatus10. In this manner, the 250 MHz and 350 MHz carrier frequencies areisolated from one another.

[0087] It will be appreciated by those skilled in the art that changescould be made to the embodiments described above without departing fromthe broad inventive concept thereof. It is understood, therefore, thatthis invention is not limited to the particular embodiments disclosed,but it is intended to cover modifications within the spirit and scope ofthe present invention as defined by the appended claims.

I/we claim:
 1. A communications apparatus for communicating multiplexedelectric signals in Ethernet protocol through one or more electric lineshaving a characteristic impedance, comprising: one or more modulators tomodulate the electric signals to produce a modulated carrier signalhaving a pre-selected frequency of about 200 MHz or greater; one or moretransmitters, each having an output impedance, operatively connected toeach modulator for transmitting the modulated carrier signals; a couplerfor connection between the electric line and each transmitter, saidcoupler matching the output impedance of the transmitter to thecharacteristic impedance of the electric line and communicating amodulated carrier signal to the electric line without significant phasedistortion; each coupler comprising: a transformer having a non-magneticcore; and a coupling capacitor that resonates with the transformer atthe pre-selected frequency; said transformer comprising: a firstconductive plate; and a second conductive plate spaced from the firstconductive plate by the nonmagnetic core; the capacitor being adapted tobe connected between the first conductive plate and the electric line,wherein the impedance of the first conductive plate and the capacitorare matched to the characteristic impedance of the electric line at apreselected bandwidth; and a frequency division multiplexer forcombining the electric signals.
 2. A communications apparatus inaccordance with claim 1 wherein said frequency division multiplexer isan orthogonal frequency division multiplexer.
 3. A communicationsapparatus for communicating multiplexed electric signals in Ethernetprotocol through one or more electric lines having a characteristicimpedance, comprising: one or more modulators to modulate the electricsignals to produce a modulated carrier signal having a pre-selectedfrequency of about 200 MHz or greater; one or more transmitters, eachhaving an output impedance, operatively connected to each modulator fortransmitting the modulated carrier signals; a coupler for connectionbetween the electric line and each transmitter, said coupler matchingthe output impedance of the transmitter to the characteristic impedanceof the electric line and communicating a modulated carrier signal to theelectric line without significant phase distortion; each couplercomprising: a transformer having a non-magnetic core; and a couplingcapacitor that resonates with the transformer at the pre-selectedfrequency; said transformer comprising: a first conductive plate; and asecond conductive plate spaced from the first conductive plate by thenon-magnetic core; the capacitor being adapted to be connected betweenthe first conductive plate and the electric line, wherein the impedanceof the first conductive plate and the capacitor are matched to thecharacteristic impedance of the electric line at a preselectedbandwidth; and a multiplexer for combining the electric signals.
 4. Acommunications apparatus for communicating electric signals withEthernet Networking protocol at about 100 Mbps or more through one ormore electric power lines having a characteristic impedance: a modulatorfor modulating the electric signals to produce a modulated carriersignal having a pre-selected frequency equal to or greater than 200 MHz;a transmitter operatively connected to the modulator and having anoutput impedance, said transmitter transmitting the modulated carriersignal; a coupler connected between the electric line and thetransmitter, said coupler matching the output impedance of thetransmitter to the characteristic impedance of the power line andcommunicating the modulated carrier signal to the power line withoutsignificant phase distortion; said coupler comprising: a transformerhaving a non-magnetic core; and a coupling capacitor that resonates withthe transformer at the pre-selected frequency; said transformercomprising: a first conductive plate; and a second conductive platespaced apart from the first conductive plate by the non-magnetic core; acapacitor adapted to be connected between the first conductive plate andthe power line, the impedance of the first conductive plate and thecapacitor being matched to the characteristic impedance of the powerline at a pre-selected bandwidth.
 5. A communications apparatus inaccordance with claim 4 wherein the modulated carrier signal is at about1 Gbps or more.
 6. A method for communicating electric signals over anelectric power distribution system including distribution transformers,the distribution system having a characteristic impedance at the inputterminal for the electric signals, said method comprising: producing amodulated carrier signal having a frequency equal to or greater than 200MHz; transmitting the modulated carrier signal through a transmitterhaving an output impedance; coupling the modulated carrier signal to theelectrical power system without significant phase distortion using acoupler that matches the output impedance of the transmitter to thecharacteristic impedance of the system at the place where the couplingis made; said coupler comprising a transformer having a non-magneticcore and a coupling capacitor, said coupler communicating the modulatedcarrier signal to the power system without significant phase distortion;and said coupling capacitor resonating with the transformer at themodulated carrier frequency; the first conductive plate; and a secondconductive plate spaced from the first conductive plate by thenon-magnetic core; said coupling capacitor being connected between thefirst conductive plate and the power system, wherein the firstconductive plate and the capacitor are matched to the characteristicimpedance of the power system at a pre-selected bandwidth; and whereinthe electric signal includes data transmitted at a speed of about 100Mbps or greater.
 7. A method of communicating electric signals inaccordance with claim 6 wherein the power system includes low voltage,mid voltage and high voltage power lines or any combination thereof. 8.A method for communicating electric signals over one or more electriclines having a characteristic impedance, comprising: producing amodulated carrier signal having a pre-selected frequency equal to orgreater than 200 Mhz; transmitting the modulated carrier signal using atransmitter having an output impedance; coupling the modulated carriersignal to the electric line without significant phase distortion using acoupler that matches the output impedance of the transmitter to thecharacteristic impedance of the electric line; said coupler comprising:a transformer having a non-magnetic core, said transformer communicatingthe modulated carrier signal to the electric line without significantphase distortion; and a coupling capacitor that resonates with thetransformer at the pre-selected frequency; said transformer comprising:a first conductive plate; a second conductive plate spaced from thefirst conductive plate by the nonmagnetic core; and said couplingcapacitor being connected between the first conductive plate and theelectric line, wherein the conductive plate and the capacitor arematched to the characteristic impedance of the electric line at apre-selected bandwidth; wherein the secondary winding of saidtransformer is operatively connected to the transmitter at a matchingimpedance of about 40 to 50 ohms substantially without regard to changesin the impedance of the electric line, and the primary of thetransformer is impedance matched to the electric line in a range fromabout 1 to 500 ohms.
 9. A system for distributing high speed informationsignals, such as digital video, digital voice, or digital data signals,over a power line distribution system including transformers from aremote location to a pre-determined location, comprising the steps of:coupling the high speed information signals into a mid-voltage sectionof the distribution system at a rate of about 10 Mbps to about 1 Gbps;distributing the high speed information signals over the power lineswithin the system including distribution transformers to a predeterminedlocation; coupling the high speed information signals from a low voltagesection of the distribution system, near the pre-determined location,into a modem for insertion into a local area network (LAN) at thepre-determined location at a speed of about 10 Mbps to 100 Mbps; eachsaid coupler comprising a transformer having a non-magnetic core forcoupling the high speed information signals without significant phasedistortion; said transformer comprising: a first conductive plate; asecond conductive plate spaced apart from the first conductive plate bythe non-magnetic core; and a coupling capacitor connected between thefirst conductive plate and the electric power line, wherein the firstconductive plate and the capacitor are matched to the characteristicimpedance of the electric power line.
 10. A method for communicatingelectric signals over an electric power distribution system withEthernet Networking protocol at about 100 Mbps or greater, said methodcomprising: producing a modulated carrier signal; transmitting themodulated carrier signal through a transmitter having an outputimpedance; coupling the modulated carrier signal to the electric powersystem without significant phase distortion using a coupler that matchesthe output impedance of the transmitter to the characteristic impedanceof the system at the place where the coupling is made; said couplercomprising a transformer having a non-magnetic core and a couplingcapacitor, said coupler communicating the modulated carrier signal tothe power system without significant phase distortion.
 11. Acommunications apparatus in accordance with claim 10 wherein thetransformer comprises: a first conductive plate; a second conductiveplate spaced from the first conductive plate by a non-magnetic core; andsaid coupling capacitor being connected between the first conductiveplate and the electric line, wherein the conductive plate and thecapacitor are matched to the characteristic impedance of the electricline at the location where the coupler is connected to the electricline.
 12. A method for communicating electric signals over an electricpower distribution system with Ethernet Networking protocol at about 100Mbps or greater, said method comprising: in a power linemodem/networking system connected to the backbone of the entireNetworking System for cable TV, telephone, internet, security and othercontrol applications being transmitted at very high speed data withdigitally signal processed carrier signals over the distribution powerline and directly through the distribution transformers from the mid tothe low voltage power line and back; producing several modulated carriersignal, thereby creating a Frequency Division Multiplexing or OrthogonalFrequency Division Multiplexing over the power line; transmitting themodulated carrier signals through a transmitter having an outputimpedance; coupling the modulated carrier signals to the electric powersystem without significant phase distortion using a coupler that matchesthe output impedance of the transmitter to the characteristic impedanceof the system at the place where the coupling is made and matches thepower line characteristic impedance; said coupler comprising atransformer having a non-magnetic core and a coupling capacitor, saidcoupler communicating the modulated carrier signals to the power systemwithout significant phase distortion.
 13. A method for communicatingelectric signals over an electric power line with Ethernet Networkingprotocol at about 100 Mbps or greater, said method comprising: in apower line modem/networking system being adapted to network very highspeed data over the power line with digitally signal processed carriersignals for cable TV, telephone, internet, security and other controlapplications; producing several modulated carrier signals creating aFrequency Division Multiplexing or Orthogonal Frequency DivisionMultiplexing over the power line; transmitting the modulated carriersignals through a transmitter having an output impedance; coupling themodulated carrier signals to the electric power system withoutsignificant phase distortion using a coupler that matches the outputimpedance of the transmitter to the characteristic impedance of thesystem at the place where the coupling is made and matches the powerline characteristic impedance; said coupler comprising a transformerhaving a non-magnetic core and a coupling capacitor, said couplercommunicating the modulated carrier signals to the power system withoutsignificant phase distortion.